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Silk fibroin (SF) is a natural protein, which is derived from the Bombyx mori silkworm. SF based porous materials are extensively investigated for biomedical applications, due to their biocompatibility and biodegradability. In this work, CO2 assisted acidification is used to synthesize SF hydrogels that are subsequently converted to SF aerogels. The aqueous silk fibroin concentration is used to tune the morphology and textural properties of the SF aerogels. As the aqueous fibroin concentration increases from 2 to 6 wt%, the surface area of the resultant SF aerogels increases from 260 to 308 m(2) g(-1) and the compressive modulus of the SF aerogels increases from 19.5 to 174 kPa. To elucidate the effect of the freezing rate on the morphological and textural properties, SF cryogels are synthesized in this study. The surface area of the SF aerogels obtained from supercritical CO2 drying is approximately five times larger than the surface area of SF cryogels. SF aerogels exhibit distinct pore morphology compared to the SF cryogels. In vitro cell culture studies with human foreskin fibroblast cells demonstrate the cytocompatibility of the silk fibroin aerogel scaffolds and presence of cells within the aerogel scaffolds. The SF aerogels scaffolds created in this study with tailorable properties have potential for applications in tissue engineering.

A green synthesis method for the preparation of polyglycidol in buffer with a high degree of control is presented. Polymerizations were conducted in phosphate buffered saline (PBS) of varying pH 3.8, 6.0, and 8.0 and deionized water at temperatures of 60, 80, and 100 °C. Taking advantage of the catalytic reactivity between water and glycidol afforded a novel green polymerization technique for the facile synthesis of polyglycidol systems with semibranched architectures with a degree of branching (DB) of 0.24, which situates the polymers between purely linear (DB = 0) and hyperbranched (DB = 0.56–0.63) systems. This method sidesteps the strenuous polymerization conditions required for most polyglycidol structures and provides well-controlled and reproducible species with a high degree of linearity and narrow polydispersities of 1.1–1.2 via the first green and nonexothermic synthesis of polyglycidol.

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Materials All reaction solvents used were HPLC quality and purchased form Sigma Aldrich. All NMR solvents were purchased from Cambridge Isotope Laboratories, Inc. and used without further purification. 2,2-bis(hydroxymethyl) propionic acid (Bis-HPA), Amberlyst® 15 Hydrogen Form (A-15), allyl glycidyl ether (AGE), anhydrous Iso-amyl alcohol (IAOH), 3,6-Dioxa-1,8octanedithiol, Nile red, Coumarin 30, and 2,2-dimethoxy-2-phenylacetophenone (DMPA) were purchased from Sigma Aldrich and used without further purification. A sulfo-cyanine 3 carboxylic acid dye (Cy3 dye) was purchased from Lumiprobe Corporation and used without further purification. Glycidol (GLY) was purchased from Sigma Aldrich and vacuum distilled prior to use. Thiol PEG Thiol (HS-PEG-SH) (1,500 g/mol) was purchased from Nanocs and used without further purification. 2,2'-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044) was purchased from Wako chemicals and used without further purification. Tin(II) trifuoromethane sulfonate, Sn(OTf)2, was purchased from Strem Chemicals Inc. and used without further purification. Teflon sheets were obtained from ePlastics. Dialysis membranes (Spectra/Por® 7, molecular weight cut-off (MWCO): 1,000 Da) were obtained from Spectrum Laboratories, Inc. 5methyl-5-allyloxycarbonyl-1,3-dioxane-2-one (MAC), and 5-methyl-5-ethyloxycarbonyl-1,3dioxane-2-one (MEC) were synthesized according to the literature and recrystallized prior to use. 1, 2 MEC/MAC copolymers were prepared according to our work previously published with molecular weights of 4000-4300 and PDI's of 1. 3 Characterization 1 H NMR and 13 C NMR spectra were obtained from a Bruker 600 MHz Spectrometer, with CDCl3/TMS or MeOD4 as the solvent. Gel permeation chromatography (GPC) was carried out with a Waters chromatograph system equipped with a Waters 2414 refractive index detector, a Waters 2481 dual λ absorbance detector, a Waters 1525 binary HPLC pump, and four 5 mm Waters columns (300 mm x 7.7 mm), connected in series with increasing pore size (100, 1000, 100,000 and 1,000,000 Ǻ respectively). All runs were performed with dimethylformamide (DMF) with LiBr (1 mg/mL) for the polyglycidol co-polymers using polyethylene glycol standards or tetrahydrofuran (THF) for the polycarbonates using polystyrene standards as the eluent at a flow rate of 1 mL/min.

a b s t r a c tIn this study, sub and supercritical CO 2 are used as effective solvents to impregnate hydrogen peroxide (H 2 O 2 ) into cellulose acetate (CA) non-woven mats. As much as 25 wt% H 2 O 2 can be impregnated at operating conditions of 25-45 • C and 1200 psig. Thermal gravimetric analysis shows that H 2 O 2 -loaded CA mats lose more than 60% of available H 2 O 2 when quickly heated to 37 • C and held at this temperature for 60 min. However, in comparison, pure H 2 O 2 -H 2 O (50:50 w/w) solution evaporates 100% within 15 min at this same temperature. Shelf-life studies show that H 2 O 2 -loaded CA mats lose ∼50% and ∼100% of available H 2 O 2 in 30 days, when stored at 2-8 • C and 20-23 • C, respectively. H 2 O 2 slowly diffuses and subsequently evaporates from the CA mat at a rate determined by the diffusion of H 2 O 2 through the CA fibers. We envision applying a thin polymer coating to the CA mat to suppress diffusional losses of H 2 O 2 , thus leading to an increased product shelf-life. These mats should find use as bandages for the continuous delivery of O 2 for advanced wound care. In vitro studies presented here demonstrate that the developed bandages produce O 2 at a controlled rate for 24 h.